1. Field of the Invention
This invention relates to a process for the production of aromatic primary amines from aromatic nitro compounds. In a particular aspect this invention relates to the preparation of an aromatic primary amine by reduction of the corresponding aromatic nitro compound with carbon monoxide and water in the presence of a basic nitrogen-containing compound which is a tertiary amine or an amide and a rhodium catalyst which is rhodium oxide, rhodium hydroxide, rhodium carbonyl including derivatives thereof or rhodium salt which forms a rhodium carbonyl under reduction reaction conditions.
2. Description of the Prior Art
The reduction of aromatic nitro compounds to primary amines with carbon monoxide and water as reducing agent in the presence of a catalytic composition comprising oxygenated compounds of at least two metals, selected from the group consisting of titanium, vanadium, manganese, iron, cobalt, nickel, copper, germanium, zirconium, molybdenum, silver, tin, antimony, lanthanum, cerum, neodymium, tungsten, gold, mercury, thallium, lead, bismuth and thorium is known from British Pat. No. 1,201,050 (Aug. 5, 1970). In this process in the reduction of nitrobenzene hydrogen and carbon monoxide are employed as the reducing agent with yields of aniline in the range of from 5 to 41% being obtained. An additional disadvantage of the process using hydrogen and carbon monoxide is that the catalytic composition is difficult and laborious to prepare.
From U.S. Pat. No. 2,671,807 (issued Mar. 9, 1954) it is known that undefined mixtures of amines are obtained by high (&gt;500 atm.) pressure reduction of aromatic nitro compounds with carbon monoxide and hydrogen in the presence of certain nickel, cobalt and ruthenium carbonyl catalysts. German Pat. No. 441,179 (Feb. 26, 1927) shows that aniline resulted from reduction of nitrobenzene in the presence of alkaline iron carbonyl solutions with the system being essentially stoichiometric.
The use of rhodium metal or certain rhodium compounds as catalysts in the reduction of aromatic nitro compounds is also known. For example the synthesis of urethanes by reaction of nitrobenzene and carbon monoxide in alcohols or phenols in the presence of [Rh(CO).sub.2 Cl].sub.2 and a Lewis acid as co-catalyst is described in British Patent 993,704 (June 2, 1965). Also the reduction of nitrobenzene with carbon monoxide in the presence of a catalyst consisting of rhodium, charcoal and FeCl.sub.3 has been reported by W. P. Hardy et. al. to yield phenylisocyanate. [See Tetrahedron Letters p. 961 (1967).]